From the Guidelines
For a 45-year-old male, I recommend ordering a morning total testosterone level as the initial screening test, as it is the most accurate and reliable assay for assessing testosterone levels 1. When ordering this test, it is essential to consider the timing, with the morning being the optimal time for drawing blood, as testosterone levels are typically highest before 10 AM.
- The patient should be in a fasting state to ensure accurate results.
- It is also crucial to document any current medications, as certain drugs like glucocorticoids, opioids, and anticonvulsants can affect testosterone levels.
- If the total testosterone level is low or borderline, it is reasonable to determine free testosterone concentrations either directly from equilibrium dialysis assays or by calculations that use total testosterone, sex hormone binding globulin, and albumin concentrations 1.
- Additionally, considering ordering luteinizing hormone (LH) and follicle-stimulating hormone (FSH) can help determine if low testosterone is due to primary testicular failure or secondary to pituitary/hypothalamic issues.
- Sex hormone-binding globulin (SHBG) may also be valuable as it affects testosterone bioavailability. This comprehensive approach provides a complete picture of the patient's hormonal status and helps determine the underlying cause of potential testosterone deficiency, guiding appropriate treatment decisions.
From the FDA Drug Label
The FDA drug label does not answer the question.
From the Research
Testosterone Tests for a 45-year-old Male
To determine the appropriate testosterone test for a 45-year-old male, several factors should be considered, including the timing of the blood draw and the measurement method.
- The study 2 suggests that morning total testosterone (TT) levels are the initial diagnostic test for androgen deficiency, but it may be possible to expand the blood draw time window for measurement of serum TT.
- The optimal time for blood draw is between 8 and 11 AM, as TT levels measured during this time differ significantly from those drawn outside this window.
- Other studies 3 and 4 discuss the measurement of total and free testosterone using liquid chromatography tandem mass spectrometry (LC-MS/MS), which provides consistently high accuracy and excellent precision for testosterone determination in human serum.
- However, studies 5 and 6 are not relevant to the question of which testosterone test to order for a 45-year-old male, as they discuss different topics such as alpha1-fetoprotein and Escherichia coli mutants.
Recommended Testosterone Measurement Methods
- Total testosterone (TT) measurement using LC-MS/MS, as described in studies 3 and 4, is a reliable method for diagnosing androgen deficiency.
- Free testosterone measurement using equilibrium dialysis coupled LC-MS/MS, as described in study 3, can also be used to assess testosterone levels.
- It is essential to consider the timing of the blood draw, with the optimal time being between 8 and 11 AM, as suggested by study 2.